The long term goal is to solve the long-standing question of how myosin functions as a motor. The principal investigator proposes to determine the biochemical defect in the myosins from cold sensitive mutants in order to uncover which part of the mechanical cycle is perturbed. He will then isolate intragenic suppressor mutations to these cold- sensitive mutants and determine the sites of reversion. He will then characterize these suppressor strains, and select some for further biochemical characterization. Finally. he will characterize biochemical myosins carrying the suppressor mutations after separation from the original cold-sensitive mutations. The principal investigator plans to confirm, modify or replace models for the various conformations that myosin assumes during its mechanical cycle.